The use of extended developer processing time (EDPT) for selected radiographic procedures can significantly enhance image detail and allow discrimination of subtle abnormalities with slight density differences. This phenomenon has been widely promoted by Dr. Lazslo Tabar as an important factor in processing single emulsion mammographic images. The dramatic improvement in contrast permits lower current settings and reduces the need for a grid for most mammographic studies. Mammography is not the only radiography procedure to benefit from EDPT. All soft tissue radiography requiring high contrast and extremity studies requiring fine bony trabecular detail can reap the benefits of this technology, whether using single or double emulsion film.
The great benefit of low voltage, single emulsion, film/screen mammography is the markedly improved contrast and image detail. When combined with small focal spots and molybdenum targets, the resulting monochromatic X-ray beam and sharp image detail provides an exceptional ability to discriminate very small objects with slight density differences. In general, the lower the voltage, the higher the contrast. The lower the voltage, the higher the current required to achieve the same film exposure. Thus, the trade off for lower voltage is higher radiation dose. Extended developer processing time can offset this need for higher current by maximizing the density of the developed image and at the same time, increasing image contrast. The result is a reduction in radiation dose (lower current and/or voltage) with enhanced contrast.
High contrast images are especially important in soft tissue radiography, such as extremity and neck films in search of foreign bodies, and neck soft tissues for evaluation of airway disease. Xeroradiography has been the accepted standard for these applications. Many institutions that have converted to film/screen mammography, continue to use Xeroradiography for these soft tissue examinations. Those without Xerographic equipment have used conventional radiographic units with standard 90 second processing, with or without some of the higher contrast films, to evaluate soft tissues. Such techniques fall short of the optimal contrast and detail possible with EDPT.
Rheumatologists are aware of the excellent bone images showing fine trabecular detail obtained with mammographic equipment, especially when using magnified small focal spot (0.1 mm) techniques. The higher radiation requirements for these studies have discouraged mammographers from subjecting their mammographic X-ray tubes to the resulting added wear and tear. Images obtained with overhead tubes using larger focal spots (0.6 to 1.2 mm) and single emulsion films can provide good soft tissue detail, but with the addition of EDPT, contrast and image detail are markedly improved. The resulting reduction in radiation requirements when EDPT is available, reduces the wear and tear on X-ray tubes, making the use of smaller focal spot mammographic equipment more feasible for soft tissue and bone detail films of the hands and feet.
Advantages derived with EDPT capability for mammography and selected soft tissue and fine bone detail studies include the following:
1. Improved contrast and image detail. PA0 2. Lower radiation dose to the patient. PA0 3. Elimination of the need to maintain an expensive second imaging technology just for soft tissues in those institutions that have converted to film/screen mammography. PA0 4. Significant reduction in "wear and tear" on X-ray tubes used for these procedures. In other words, longer tube life and reduced overhead. PA0 5. Added imaging capability and improved service to referring clinicians.
Accordingly, it is an object of the present invention to provide improved X-ray film development when used on soft tissue such as in mammography.
It is another object of the present invention to provide existing single speed X-ray film processors with a dual speed capability for improved X-ray image detail and resolution.
Yet another object of the present invention is to provide an easily installed, inexpensive kit for retrofit installation in existing single speed X-ray developers to provide an extended developer processing time.
Still another object of the present invention is to provide a continuous range of reduced speeds for an X-ray film developer for improved contrast and image detail.
A further object of the present invention is to provide an extended development processing capability in existing single speed X-ray film processors at a very modest cost with the added benefits of reduced radiation exposure to the patient and prolonged life of expensive X-ray tubes.
Although new processors are available with dual speed controls that allow processing at the usual 90 seconds and/or EDPT, the cost of replacing an existing processor or adding one of these dual speed units is substantial and frequently prohibitive. Few facilities can afford the luxury of a dedicated processor just for EDPT. A cost effective alternative is the relatively inexpensive EDPT conversion kit of the present invention which can be easily installed by any processor servicing technologist. This device modifies existing processors to run any given film at the standard 90 seconds or any preselected extended developer processing time. The conversion unit is available for most Kodak processors and may be adaptable to other manufacturers, units also. With the conversion of a typical busy processor, handling over 400 sheets of film daily, the converted processor is capable of processing a mix of mammographic, soft tissue and bone detail films with EDPT together with conventional radiographic films processed at 90 seconds. Films processed at different speeds can be alternated. Selection of EDPT for a given film is made simply by the press of a button on an illuminated panel indicating the development time. The unit immediately reverts to 90 second mode when the EDPT film leaves the developer, resulting in no significant delay between films. If the unit is being used primarily for films processed with EDPT, the "standard"0 mode can be set for EDPT with push-button selection for the 90 second mode.